MIM Jazz: Questions on Mods & tweeks

Discussion in 'Hardware, Setup & Repair [BG]' started by Skip, Jan 3, 2001.

  1. Skip


    Mar 22, 2000
    Bronxville, NY
    I just got a MIM Jazz and I love it - but I'm a audiophile nut at heart and can't help but to wonder if changing a few things around would make things sound much better. Here are my questions about some mods and tweeks:

    1) The Bridge - OK, pretty much everyone says to replace the stock bridge. Most people here seem to suggest a drop in from BadAss or GOTOH. What about through body bridges? Will a MIA Fender Bridge fit on a MIM (plus the holes and ferrules)?

    2) The Pick-ups - Same here, consensus is to change these too. No questions, on this one and I'll ask in the pick-up topic if I do.

    3) Shielding - I've read that most electric instruments are badly shielded, and I've seen a web page on shielding an instrument (it was a Str#t, but the general principles should apply.) Has anyone here actually done it? How big is the improvement?

    4) The Pots and the Tone Cap - Related to #3, I take it that the quality of the parts used is less than state of the art. Has anyone replaced the pots or the tone cap? The tone cap is listed by Fender as a 0.05uF, I assume this is a 0.047uF cap. Is there room in the body cavity for much modification? I'm thinking of fitting a larger polypropylene cap in its place.

    Thanks in advance.


    [Edited by Skip on 01-03-2001 at 02:06 PM]
  2. oddentity

    oddentity Supporting Member

    Nov 20, 2000
    Chris, I own two MIM Jazzes and here's what I did:

    (1) The Bridge - I replaced the stock bridge with a Gotoh 206. It needs extra drilling, so if the idea of drilling into your bass bothers you it might not be the best bridge for you. On the other hand, it will accomodate thru-body stringing as well as on the bridge. I plan to drill holes for thru-body stringing but haven't gotten around to it yet. Personally I think it's a great bridge- very tweakable and very stable.

    (2) I went for Dimarzios on my fretted; not sure yet what I'm going to do with the fretless.

    (3) I still haven't addressed this problem...

    (4) I replaced the pots with new ones from Stewart MacDonald. They have a much more robust feel to them. I also changed the tone cap, but for the life of me I can't remember the cap value. I just went to Radio Shack, bought a bunch, and switched them in and out until I found one I liked. The cap I ended up using was significantly larger than the stock cap, but not so large as to make space an issue. I also replaced the stock knobs with chrome domes, which classes the bass up a bit!

    Hope this helps!!
  3. dytakeda


    Jul 18, 2000
    I just got the MIM Jazz Fretless, and like you, I think it's great.

    Bridge - I don't see any reason to change the bridge. I know that's not the consensus around here, but there's really nothing I can see that's different on this one compared to the "classic" Fender bridge. Bridges with cast plates like the Gotoh sound different, but that doesn't mean they sound better. That thin plate is part of the Fender sound. Use your ears. If you want a different sound, try changing the bridge. Don't do it because everyone else says to.

    Pickups - I'll probably change these eventually, depending on how much time the fretless actually gets played.

    Shielding - This is something I can speak to you about from experience. I did this on the day after I brought it home. This makes a WORLD OF DIFFERENCE. One of the cost reductions on the MIM is that the neck pickup cavity and the control cavity are connected by a channel across the top of the bass, which is covered by the plastic pickguard. The underside of the pickguard is not shielded at all, so all the extraneous electical noise hits those wires and goes straight to the amp. This is the one mod that all instruments should get if they don't come with it.

    PS - I haven't shielded the bridge pickup cavity yet, and I still got a tremendous improvement. That body route covered by the plain plastic pickguard is the main source of noise. The main reason I haven't tackled the bridge pickup is because it's a very tight fit. The wood is routed to fit the shape of the pickup, unlike the neck pickup where it's a bigger rout.
  4. As for the shielding thing, it ain't necessary if you have hum-bucking pickups. And hum-bucking pickups do a lot more for killing buzz than shielding a bass with single coil pickups. Most of the humm comes from the pickups, not the wires, hence the name "pickups". :D Use proper wire routing methods (twist corresponding pairs of wires together) and shielding isn't necessary with hum-buckers.

    Neither of my Jazz basses are shielded, both are hum-free since I have hum-buckers on both.

    New hum-bucking jazz pickups (Dimarzio DP123's for me and my thin wallet-$90, Seymour Duncan Classic Stack Jazz's if you got $150 to put into pickups) make a world of difference in the sound, too.

    I have not changed any pots or caps on mine and I don't plan on it.

    I do change the bridge, 'cause they are dinky. I understand that they contribute greatly to the "Jazz" sound, but a new bridge does wonders too, and I like the sound they add. I did not see the need to go through-body with my strings, it may or may not help things.

    Mine + Badass2 + Dimarzio DP123's + D'Addario EXL165's


  5. dytakeda


    Jul 18, 2000
    I hate to disagree with someone in a forum like this, but the idea that shielding is not necessary with humbucking pickups is just wrong. Humbucking pickups eliminate 60 cycle hum, and it's just that: "Humm". throbbinnut is correct when he says that hum comes from the pickups. The reverse wound coils will cancel out the hum. This works because the hum is the result of a given frequency. However, they will also sound different than single coils. The difference in sound depends on the design.

    Shielding, on the other hand, is intended to eliminate noise, and by that I mean electical noise which will translate into noise we can hear. Think of noise as static, and you'll understand why a humbucker can't eliminate that. There's no frequency to cancel. Take a look underneath the P-Bass' humbucking pickup: there's shielding. The Les Paul guitar humbuckers usually have shielding over the top of the coils. Humbucking and Shielding are two completely different solutions to two different problems.

    If your instrument isn't factory shielded, adding it is the most cost effective improvement you can make. <== Take this statement to the bank. It's as good as gold.

  6. Skip


    Mar 22, 2000
    Bronxville, NY

    I left out the pick-up issue on purpose. I like the overall sound of the bass, I just want to calm down the hum and noise. My ultimate mod would be to create a completely balanced circuit and replace the 1/4 in jack with a XLR conection. :)

    dytakeda, how did you shield your bass? Copper foil or paint?

    throbbinnut, nice picture - mine's black.

    Also how does the bridge change the tone? Not the physics, how does it sound?

    Thanks for the responce so far.

  7. rllefebv


    Oct 17, 2000
    Newberg, Oregon
    My MIM Jazz is a '92, so I know that some of the construction issues are different, but here goes...

    Like dytakeda, I am partial to the thinner Fender bridges, though I can certainly understand the logic of going with a cast bridge like the Gotoh. I changed my original bridge for one of the Fender types from StewMac, as it was EXCESSIVELY thin. The replacement is somewhat thicker, but still allows the bass to speak in a way that I find appealing...

    I sheilded with copper tape, the control cavity and underneath the pickguard. Yes it made a huge difference, though this time around I am going with conductive paint, available from StewMac, (I just know that I'm putting somebody's kid through college!!!)...

    In the next month or so, I am giving this bass an overhaul which will include the following...

    New tuners...Hipshot UltraLites
    New pickups...Schaller JBX
    Fill in the 'tub' and connecting routes around the neck pickup with wood. I hate the way these are routed!
    Mod the existing bridge and body to accept through-body stringing.

    Maybe I'll strip and refinish it too...haven't decided this one yet. I'll probably redo the electronics. I used to have an 'all controls bypass' which sent the signal from the pickups straight to the output jack. I needed the pot for another bass I was working on, so I'd like to re-incorporate this into this bass again.

  8. Agreed that the humbuckers cancel hum, and they will sound different than single coils. Les Paul vs. Fender Strat sounds are an example. That stuff about it working because it is a certain frequency is wrong, though. All noise whether it is steady hum or spurious noise has frequency content. Humbuckers do not work based on frequency cancellation, they work by phase cancellation. Shielding is definitely a different animal from humbucking, though, as you say. I still think shielding is not NECESSARY with humbuckers, and I will explain why.

    You are right in the fact that shielding and humbucking are totally different. Hum bucking works by using 2 coils reverse wound, and 2 magnets reverse-poled. Any signal generated by changes in the pickup's SELF-GENERATED magnetic field induces a voltage at the output. Any signal induce from outside sources is cancelled. Here's the trick, when you reverse wind one of the coils, now it's voltgage is 180 degrees out of phase with the other coil, since they are wound opposite each other, this is true whether the signal is from the strings or outside noise sources. This would result in no noise and no sound at all from the strings, since the 2 signals would cancel. So, flip one of the magnets over, now you have in essence a mathematical double-negative on one of the coils, since flipping the magnet puts the signal out of phase and reverse winding the coil reverses the phase again, so the result is that the string-generated signals ONLY are back in phase with the other winding. So now you are back at 2 times the original single coil signal for the string signals, but the noise signals still cancel. Here's the trick, any externally generated noise signal, whether it is hum or MAGNETICALLY coupled static, pops, whatever, will create 2 equal and opposite signals in the 2 coils that will then add to 0. The string generated signals are reversed twice to be back in phase.

    Shielding is effective on all ELECTRICAL coupled noise, not magnetic coupled noise. Electrical coupling is like how a capacitor works, and magnetic coupling is how an inductor or transformer works. Electrical kind of goes with voltage, magnetic kind of goes with current. In my experience, hum-bucking pickups get rid of practically all the noise, since most of it is magnetically coupled into the coils of the pickups, far less is electrically coupled into the system. Granted they are different, and shielding does do something that hum-buckers can't. But, hum-bucking does something shielding cannot do, and that is cancel out magnetically induced noise. Since the pickups are more sensitive to magnetic noise than the wires and pots are to electrical noise, I treat them first.

    Example: Microphone cables have 3 conductors and do not have to be shielded to be noise-free. One conductor is common, one is signal positive, and the other is signal negative. Both signal lines pick up equal in-phase noise, but at the receiving end they are subtracted from one another, this cancels the noise and doubles the wanted signal. This is a balanced line configuration. First cousin to hum-bucking.

    I see your point that shielding is different, but in my experience, hum-bucking pickups do not need shielding to be noise-free and hum-free. Best situation? Shielding and humbuckers.


    [Edited by throbbinnut on 01-04-2001 at 08:16 AM]
  9. dytakeda


    Jul 18, 2000
    Throbbinut -
    So we do agree! I understand and agree with everything you stated. The main reason that shielding is so important (IMHO) is that you can't control your environment. My opinion may be so strong towards shielding because the room I practice in is "noisy". There's no dimmers, but the wiring in this room just plain sucks. Shielding made a huge diference in all the basses I've had. I'm mainly a P-bass kind of guy, too, which are humbuckers, and I still got noise in this room and on certain areas of certain stages facing certain directions. <G>

    Skip -
    When I shielded my most recent bass, believe it or not I used brass. I bought a package of shim stock at a hobby store. It came in various thicknesses, but all very thin. I formed large sections of it by folding against a straight edge. This worked out well because the MIM Jazz has three main areas which are largely rectangular in shape. I was able to cover the bottom and sides of the three main areas with a single piece of brass each. After forming, I stuck it to the inside of the cavity with double sided scotch tape. Making the smaller pieces for the rounded ends of the control cavity, etc. was more difficult, but made easier, I think, by the stiffness of the material.

    Trying to describe how a bridge changes the sound is almost impossible. I like to say that with the thin plate, you "get more wood" in your tone. I think the thicker plate gives you a stronger initial attack, but the overall tone is a bit more sterile, less organic. That's the best I can do with the description.

    I'm in on this discussion because of my MIM Fretless J. I want this thing as woody as possible (ala Jaco). So, the less metal I put between the strings and the wood, the closer to that goal I'll be.

  10. re. point 4; tone pot capacitor value:
    In a book I've got, Dan Armstrong suggests changing the capacitor to 0.022uf "it yields a Jaco Pastorius-like tone"(on a J Bass, naturally).
    I've fitted them to my P-basses, and they let more mids through when the pot is rolled off than the stock value- almost like a mid boost.

    another mod worth considering is a controls bypass switch as a push/pull pot, either on each volume control, or on a master vol control. it allows a bit more brightness in bypass mode.

    [Edited by The Mock Turtle Regulator on 01-04-2001 at 01:31 PM]
  11. I understand completely. You and I both are talking out of experience, and you've played where shielding was still necessary, and I've never had that problem. I'll stick that in my bag of tricks to use when needed though for sure. I'm just so damn lazy, the thought of doing all that shielding just makes me cringe. :D

    Rock on,
  12. dytakeda


    Jul 18, 2000
    Here's a site I found yesterday which preaches the gospel of shielding: http://www.guitarnuts.com

    All the explanations are regarding Strats and Teles, but the theory's the same. This guy goes way past what I normally do and discusses the elimination of ground loops and the application of star point grounding.

    You can find almost anything on the net!
  13. Skip


    Mar 22, 2000
    Bronxville, NY
    That is the site I linked in my first post. See what happens when I get fancy with the coding? ;)

    Which book? Where did you find it? Remember that on a passive instrument you can only cut not boost freqs. The web site dytakeda and I linked explains how the tone controls work (though I only half understand the explanation).

    I appreciate the input. I will probably have to shield my bass as I practice in my home office with all kinds of electrical equipment going.

    As an aside, most cables are shielded - even mike cables. The ground is usually used as the shield in most cables I've seen. The only unshielded ones I've ever seen are Kimber Kable interconnects. I could be wrong, as I've never taken any equipment cables apart.
  14. The book I got that tip from was "Electric Bass Guitar", which is made up of various articles from Guitar Player and Bass Player magazines. It also has diagrams for wiring a Jazz bass with a series/parallel switch.

    I said "almost like a mid boost", as the tone does change noticeably with this capacitor when the tone is rolled off completely- it gives the illusion that the mids have been boosted- in reality probably all that's happened is that the mids are just more noticeable since the highs have been rolled off to ground through the capacitor.
    My understanding is that the smaller the value of the capacitor, the higher the frequency that gets rolled off to ground ie. removed from the signal.

    Gibson EB3's had a midrange circuit using a choke/inductor of some kind, which I might try out sometime.

    re. shielding, I've used self-adhesive aluminium foil to screen the control and pickup cavities of my P-basses. it's probably not as good as brass, and you can't solder ground wires to it, but it seems to do the trick.

    one area I'm unsure of is the ground wires linking each control pot casing- the pots are also linked by contact with the foil on the back of the scratchplate- a possible hum loop scenario?

    [Edited by The Mock Turtle Regulator on 01-07-2001 at 10:33 AM]
  15. dytakeda


    Jul 18, 2000
    Mock Turtle asked:
    one area I'm unsure of is the ground wires linking each control pot casing- the pots are also linked by contact with the foil on the back of the scratchplate- a possible hum loop scenario?
    On the site guitarnuts.com, cutting the connections between the backs of the pots is specifically mentioned to eliminate ground loops.

  16. :oops: ...I should have checked out that site first.
    that's the first time I've seen anyone else mention ground loops being caused that way- every wiring diagram I've seen recommends wiring the pot cases together. I suspected this might be a problem a few years back and scored lines in the foil on the scratchplate of my P-bass Plus to break the loops(probably not the best way to do it, but I figured that the grounding by wires soldered to the pots would be more reliable than mere contact to the foil) but didn't notice any difference (any improvement was'nt noticeable when compared to the hum coming from the bridge Jazz single coil pickup) , so I opted for the stock arrangement (pot cases wired together and foil) on the P-bass I built from Warmoth parts recently, and the only hum is when the bridge pickup is set to single coil operation- so no difference, really.

    It's arguable that any ground loops caused are hardly noticeable if the cavity is screened anyway, but I'll have to experiment with the guidelines on that site to see if there's any improvement to be gained.

    [Edited by The Mock Turtle Regulator on 01-08-2001 at 05:14 PM]
  17. BernardJohnson


    Jan 9, 2001

    I have a MIM Jazz bass.....it is white with a rosewood neck
    here are my upgrades:

    Baddass II bridge
    Seymoure Duncan Bassline 3/4lb pickups
    Grover tuners- (great tuners)
    dark pearl pic-shield
    DR-LoRiders (45-105)

    And with those upgrades I'm very pleased.....

    keep playing...BJ
  18. dytakeda


    Jul 18, 2000
    Just curious... how much $$$$ did you put into these upgrades? I'm guessing around $230 or so (not counting the strings) Everyone changes those eventually.

    On the subject of strings, anybody have any thoughts on why Fender puts big, gigantic flatwounds on the MIM fretless, but rounds on the AmStd? I think of fretless jazz, and I hear Jaco-like tones. Does Fender not hear the same music we do? I bought my MIM fretless without really hearing the sound I was after. The body seemed resonate, so I figured that rounds would sing, and they did. I wasn't knocked out by the sound before I bought it, and don't you think I should have been?

  19. Rumblin' Man

    Rumblin' Man Banned

    Apr 27, 2000
    Route 66
    The MIA Jaco Signature Model comes with flats on it, so maybe not.
  20. NoNoise

    NoNoise Supporting Member

    Mar 5, 2005
    New Jersey
    This is a pretty cool thread. I think I'll bring it back to life. Anyone else care to comment on changing the bridge from the stock MIM bridge. I've been thinking about going with the Gotoh
    ( http://www.basspartsresource.com/bridge_gotoh.htm ),
    But I don't want a less "organic" sound.